Navigation method and system for autonomous machines with markers defining the working area

ABSTRACT

A method for automatically operating a robot, attached to a lawnmower or other unmanned machine, within an enclosed area is disclosed. The method includes the steps of: 1) providing the following elements: a proximity sensor positioned on the robot, a boundary along the perimeter of the working area and along the perimeter of each area enclosed in the working area in which the robot should not operate, the boundaries being detectable by the proximity sensor, a processing unit connected to the proximity sensor and receiving an input therefrom, a navigation unit on the robot to determine the coordinates of the robot relative to an arbitrary origin, a direction finder, and a memory to store values generated by the processing unit; and 2) causing the robot to move along each of the boundaries provided around or within the working area, to detect the boundaries and to memorize their shape, and to store in the memory values representative of the coordinates of the boundaries, thereby to generate a basic map of the working area. When the robot is to operate within the area, the method includes the steps of: (a) causing the robot to start from a starting point having known coordinates within the basic map of the working area; (b) continuously determining the coordinates of the robot by analyzing data obtained from the navigation unit and by detecting the vicinity of a boundary; and (c) correcting the actual position of the robot on the basic map by comparing the calculated and the actual coordinates of each detected boundary.

FIELD OF THE INVENTION

[0001] The present invention relates to a method and related systems fornavigation in an enclosed area. More particularly, the invention relatesto method and apparatus which can be used to cause an automated deviceto move and to perform predetermined tasks within an enclosed area.

BACKGROUND OF THE INVENTION

[0002] The use of automated devices is widespread nowadays, and findscountless applications. For instance, robots perform very precise anddelicate tasks in the construction of electronic devices, or in medicineand aviation. Robots are also used in uses which require motion,notably, for automatic warehouses, where goods are retrieved and storedby means of computer-actuated robots. Other applications include, e.g.,fetching raw materials in the course of industrial manufacturing, andremoving and packaging finished pieces. In everyday's life, attemptshave also been made to exploit robots for lawn mowing and for vacuumcleaning.

[0003] The major drawback of mobile robots, which the art has so farbeen unable to overcome, is the fact that their movements are limited towell predefined paths, normally requiring that they move along rails, orthat they be provided with expensive navigation signs, positioned withinthe area in which they move, which operate as “stations” which redefinethe exact position of the robot, and from which the program may directthe robot to the next station. These intermediate signs are expensive,take up space, and are inconvenient to use, since they must be veryprecisely positioned and cannot be easily moved.

[0004] Another approach involves providing an area delimited byboundaries recognizable by the robot, and permitting the robot to effecta random walk therein, during which random walk it carries out itstasks. This approach entails severe drawbacks: first of all, when therobot moves within a predefined area by random walk, there is no way toensure that the whole area will be covered by the tool which mustoperate thereon. As a result, even though the robot may operate for along period of time, unworked areas may be left at the end of theoperation. Secondly, if the area to be worked is irregular, or if itpresents “islands ”, viz. areas which must not be worked, the randomwalk may lead to imperfect operation around such islands, as well as atthose locations where the perimeter is of irregular shape. Thirdly,because the operation of the robot is not programmed to obtain apredetermined coverage, it is necessary to allow the random walk to goon for a long period of time, so as to increase the chances of coveringa major portion of the area to be worked. This is not only energyconsuming, but also leads to an increased wear of the equipment, and mayalso be environmentally undesirable due, e.g. to noise or otherpollution caused by the operation of the robot. Even if the robot isoperated by sun energy, most of the aforesaid problems are not overcome,and additional problems exists, connected with such a mode of operation.For instance, the robot may not work properly in areas of the worldwhere sun radiation is scarce or low, and may be inoperative forsubstantial parts of the day, e.g., on cloudy weather.

[0005] A further approach involves preprogramming the robot with ablueprint of its designated area of operation, such as a floor map of abuilding in which a robot is to operate. This approach has two majordrawbacks:

[0006] a) it requires preprogramming by the user, which makes inunpractical for extensive consumer use; and

[0007] b) it requires that such preprogramming is repeated each timesomething changes in the work area.

[0008] It is therefore clear that it would be highly desirable to beable to provide means by which automated mechanisms may move and performtheir task within a predetermined area, without being hindered by theneed for predefined paths and rails, or by intermediate navigation signsor preprogramming, and which may carry out their task in a predeterminedmanner, without relying on random occurrences and/or on unstable energysources.

SUMMARY OF THE PRESENT INVENTION

[0009] It has now been found, and this is an object of the presentinvention, that it is possible to free automated mechanisms operatingwithin an enclosed zone from the need for preprogramming or predefinedpaths and rails, and from the need for intermediate navigation aids, andthis to overcome the drawbacks of the prior art and to provide means bywhich a robot may perform its tasks within an enclosed area in a mannerfree from such limitations, with high precision and in a minimal periodof time.

[0010] It is an object of the present invention to provide a navigationmethod which fulfills the aforementioned goals.

[0011] It is another object of the invention to provide means which canbe used in systems utilizing the method of the invention.

[0012] Other objects of the invention will become apparent as thedescription proceeds

[0013] The method for automatically operating a robot within an enclosedarea, according to the invention, comprises the steps of:

[0014] providing a boundary along the perimeter of the working area, thesaid boundary being detectable by a proximity sensor;

[0015] providing boundaries along the perimeter of each area enclosed inthe working area, in which it is desired that the robot should notoperate, the said boundaries also being detectable by a proximitysensor;

[0016] providing a proximity sensor positioned on the robot;

[0017] providing processing means connected to the said proximity sensorand receiving an input therefrom;

[0018] providing location means on the said robot, to determine thecoordinates of the robot relative to an arbitrary origin, at anyspecific time;

[0019] providing direction finding means;

[0020] providing memory means to store values generated by the saidprocessing means and, optionally, by the said location means;

[0021] causing the robot to move along each of the boundaries providedaround or within the said working area, to detect the said boundariesand to memorize their shape, and to store in the memory means valuesrepresentative of the coordinates of the said boundaries, relative to anarbitrary origin, thereby to generate a basic map of the working area;

[0022] when the robot is to operate within the said area:

[0023] (a) causing the robot to start from a starting point having knowncoordinates within the basic map of the working area;

[0024] (b) continuously determining the coordinates of the robot byanalyzing data obtained from the location means and by detecting thevicinity of a boundary; and

[0025] (c) correcting the actual position of the robot on the basic mapby comparing the calculated and the actual coordinates of each detectedboundary.

[0026] By “robot” it is meant to indicate any autonomously operatingdevice, which may carry out pre-programmed tasks with one or more tools,while moving in the process from one location to another

[0027] According to a preferred embodiment of the invention, thelocation means comprise movement measuring means, such as an odometer orthe like device, to measure the distance traveled by the robot, e.g., bymeasuring the number of revolutions of a wheel. As stated, directionfinding means are also provided, so as to provide information on thedirection in which the robot travels at any given time, which is neededin order to determine the coordinates of the robot on the map. Thedirection finding means can be of any suitable type, e.g., may comprisea compass.

[0028] While, as stated, it is an object of the invention to utilizerelatively inexpensive devices for the operation of the robot, it is ofcourse possible to employ more expensive and sophisticated equipment,without exceeding the scope of the invention. Thus, for instance, it ispossible to employ range-finding means, such as a laser range-finder orRF range finders, to determine the distance of the robot from one ormore given locations, at any given time, instead of, or in addition to,using an odometer or the like device to measure the distance traveled.However, any such modifications will be apparent to the skilled person,and therefore are not discussed herein in detail.

[0029] According to a preferred embodiment of the invention, theboundary which is detectable by a proximity sensor comprises a metallicwire through which electric current flows, and the proximity sensorcomprises a magnetic field detector. According to another preferredembodiment of the invention, the boundary which is detectable by aproximity sensor comprises passive metallic means which is excitable bya magnetic field, and the proximity sensor comprises an electric fielddetector. In still another preferred embodiment of the invention theboundary which is detectable by a proximity sensor comprises passivemagnetic means, and the proximity sensor comprises a magnetic fielddetector. Of course, the boundary may be marked by continuous or bydiscontinuous marking means, or by combinations thereof.

[0030] In still another alternative embodiment of the invention, theboundary which is detectable by a proximity sensor comprises a guidewire through which an acoustic signal passes, and the proximity sensorcomprises an acoustic detector.

[0031] A further improvement in the precision of the determination ofthe actual coordinates of the robot on the map, at any given time, canbe obtained by further providing on the boundaries a plurality ofindividually recognizable markers. Thus, when the robot reaches theboundaries, it not only identifies them by the proximity sensor, but mayalso receive the exact coordinates on the boundaries assigned to thespecific marker it has detected. According to a preferred embodiment ofthe invention, when provided, the markers are substantially located ateven distances from one another. Suitable markers will be easilyrecognized by the skilled person, and may comprise, e.g., an RF tag ormagnetic tag.

[0032] As stated, according to another preferred embodiment of theinvention, the distance-measuring means comprise an odometer or the likedevice, coupled to the wheels of the robot.

[0033] As stated, the robot, when initialized, moves along theboundaries and memorizes their shape. Such memorization may be carriedout in a number of ways. For instance, the shape can be memorized bytaking continuous or discontinuous readings of the compass and theodometer, and any such readings are then continuously integrated, togive the full coordinates of the boundaries.

[0034] The method of the invention can be exploited in a variety ofuses, and is not limited to any particular field of application. Oneparticularly interesting use, however, to which reference will be madealso hereinafter for the purpose of exemplification, is when the robotis coupled to a lawn mower. Such robot permits to mow the lawn in theabsence of the owner, and at any suitable time, or to vacuum clean anypredetermined premises.

[0035] Of course, safety means should preferably be provided to ensuresafe operation of the robot. for instance, automatic shut-off of therobot should be provided, coupled to logic circuitry, to ensure that theoperation of the robot is discontinued if one of a number ofcontemplated possibilities takes place. for instance, if the measureddistance traveled without encountering a boundary exceeds by a thresholdvalue the maximal linear distance within the bounded area, as calculatedfrom the map of the boundaries, this may mean that the robot has exitedthe boundaries due, for instance, to a malfunctioning of the system dueto which the proximity sensor has failed to identify the boundary. Otherrequired safety means will be easily recognized by the skilled person,according to the type of robot and the intended use thereof.

[0036] The invention is further directed to an automated robot foroperation within an enclosed area, comprising:

[0037] a proximity sensor positioned on the robot;

[0038] processing means connected to the said proximity sensor andreceiving an input therefrom;

[0039] location means, to determine the coordinates of the robotrelative to an arbitrary origin, at any specific time;

[0040] direction finding means; and

[0041] memory means to store values generated by the said processingmeans and, optionally, by the said location means.

[0042] The term “proximity sensor”, as used herein, indicates any devicewhich is capable of detecting that the boundary of the working area isnear. This may include, e.g. magnetic field detectors, acoustic signaldetectors, bar code readers, resonance tag meters, transceivers, etc

[0043] The invention also encompasses a system for automaticallyoperating a robot within an enclosed area, comprising:

[0044] boundary means suitable for positioning along the perimeter ofthe working area, and of each area enclosed in the working area, inwhich it is desired the robot not to operate, the said boundary meansbeing detectable by a proximity sensor;

[0045] a robot provided with a proximity sensor;

[0046] processing means on said robot, connected to the said proximitysensor and receiving an input therefrom;

[0047] distance-measuring means on the said robot, to measure thedistance of the robot from a given starting point, at any specific time;

[0048] direction finding means;

[0049] memory means to store values generated by the said processingmeans and, optionally, by the said distance measuring means and/ordirection finding means; and

[0050] motion means, to cause the robot to move.

[0051] In accordance with a further embodiment of the invention, amethod for automatically cutting a lawn is provided. The method includesthe steps of:

[0052] providing a lawnmower with a robot and at least a plurality oflawn height sensors;

[0053] cutting a first swath of lawn in a first direction;

[0054] performing a maneuver, under control of the robot and in responseto output of the lawn height sensors, in a second direction generallyopposite of the first direction to bring said lawnmower to a locationparallel to but overlapping the first swath by a predeterminedpercentage as indicated by the different output of the lawn heightsensors;

[0055] cutting a second swath of lawn parallel to the first swath whilecontinually monitoring the lawn height output of said lawn heightsensors thereby to ensure that the percentage of overlap is generallymaintained;

[0056] repeating the steps of performing a maneuver and cutting a secondswath for further swaths of lawn, wherein the previously cut lawn isdenoted by said first swath of lawn and the swath to be cut is denotedby the second swath of lawn.

[0057] The maneuver can be an S-shaped maneuver and the grass heightsensor can include the following elements:

[0058] a housing;

[0059] a rotatable wing against which grass can push, the wing having apin attached thereto;

[0060] a fixed second pin, connected to the housing;

[0061] a spring attached around said pin, wherein the ends of the springpress against opposite sides of the wing and opposite sides of the fixedpin, and

[0062] means for measuring the angle of rotation of the rotatable wing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0063] The present invention will be understood and appreciated morefully from the following detailed description taken in conjunction withthe drawings in which:

[0064]FIG. 1 schematically shows an enclosed area within which a robotmust operate, the shaded areas representing “islands” in which the robotmust not enter;

[0065]FIG. 2 shows, in cross-section, a boundary of FIG. 1, according toa particular embodiment of the invention;

[0066]FIG. 3 (A and B) illustrates the method of the invention, usingpolar coordinates;

[0067]FIG. 4 illustrates the method of the invention, using Cartesiancoordinates;

[0068]FIG. 5 (A and B) is a flow-sheet of an example of a locationcorrection process, according to one preferred embodiment of theinvention;

[0069]FIG. 6 is a flow chart of the operation of a system, according toone preferred embodiment of the invention;

[0070]FIG. 7 is a pictorial illustration of a lawnmower following theline of cut grass, constructed and operative in accordance with afurther preferred embodiment of the present invention;

[0071]FIG. 8 is a flow chart illustration of a method of operating thelawnmower of FIG. 7;

[0072]FIG. 9 is a pictorial illustration useful in understanding themethod of FIG. 8;

[0073]FIG. 10 is a schematic illustration of a lawn height sensor,useful in the method of FIG. 8;

[0074]FIGS. 11A and 11B are schematic illustrations of a lawnmower, asensor and two types of boundary markings, forming further embodimentsof the present invention; and

[0075]FIGS. 12A, 12B, 13A, 13B, 14A, 14B, 15 and 16 are schematicillustrations of various types of boundary markings useful in theembodiments of FIGS. 11A and 11B.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0076] The present invention will be better understood through thefollowing illustrative and non-limitative description of preferredembodiments.

[0077] Looking now at FIG. 1, the working area in which the robot mustoperate, indicated at “A”, is enclosed by a boundary 1. Within theworking area there are “islands” in which the robot must not penetrate,which are shadowed and enclosed by boundaries 2 and 3. According to oneembodiment of the invention, the robot is an automated lawn mower, andthe area A is a lawn. Islands 2 and 3 may be, e.g., trees and theirvicinities or flower beds. Thus, we wish the mower to operate only inareas in which grass grows, and to avoid other areas. Alternatively, therobot can be coupled to a floor sweeper or a floor polisher or any otherdevice which has to scan a flat surface.

[0078] As stated, according to one particular embodiment of theinvention, the boundaries 1, 2 and 3 may comprise a conducting wire.This type of boundary is shown in cross-section in FIG. 2, which shows awire 4, comprising a metallic core 5 and a plastic outer layer 6. Acurrent “i” is caused to flow through the wire, thus generating amagnetic field along the wire. The intensity of the current may be verylow, since it is not necessary that the magnetic field be sensed at agreat distance from the boundary, and it is sufficient that it be feltin the close vicinity of the wire. The magnetic field is sensed,according to this particular embodiment of the invention, by a magneticfield sensor provided on the lawn mower. The magnetic field and thesensor to sense it are conventional and well known in the art, andtherefore are not described here in detail, for the sake of brevity.

[0079] Taking the lawn mower as an example, but it being understood thatthe invention is in no way limited to its use with a lawn mower, or withany other particular device, the invention operates as follows. Acoordinates system is defined, as well as a starting point. FIG. 3Ashows a lawn mower L relative to the starting point “S” within the lawn,the lawn mower L being at a point (Θ, r) viz at a distance r, which ismeasured by measuring the movement of the mower, and at an angle Θ fromstarting point S, which is measured by means of a compass. Thus, asshown in FIG. 2B, any point within the enclosed area S will have aunique polar coordinate.

[0080] When it is desired to teach the robot the boundaries of its task,the lawn mower is caused first to move around the boundary 1 of FIG. 1.The memory means of the robot memorize the coordinates of the boundary1, relative to starting point S. Throughout this teaching movement, theboundary sensor positioned on the robot (not shown) senses the boundary1. Similarly, the boundaries 2 and 3 are sensed for the first time bythe robot, and memorized for future use. The robot now has an initialmap of the area, similar to what is shown in FIG. 3B, each point havingbeen assigned a coordinate. The set of coordinates so created will betermed “the map” of the working area.

[0081] When it is desired to mow the lawn, the robot is brought tostarting point S, and it is started according to a set of instructionswhich has been pre-programmed, and which may be different for eachdifferent task. For instance, a circular lawn may be better looking ifmowed in circles, while a soccer field requires back-and-forth mowing.An automated lawn mower according to the invention may further beprovided with a number of pre-set programs, from which the user canchoose.

[0082] The robot, as said, is further provided with distance-measuringmeans, such as an odometer or the like device. However, these devicesare not fully accurate, and may provide only approximate distance valuesfor any given position. The error in the measurement of the distance mayderive from a variety of reasons, e.g., the slipping of wheels on amoist lawn, uneven ground, etc., and the error may build up to quite asubstantial extent, impairing the ability of the robot to complete itstask with a high degree of precision. While, of course, precisemeasuring means exist, such as laser distance measurements, these areexpensive and/or require calibration targets located in or around theworking area. It is a purpose of the invention to avoid the use of suchexpensive and complicated distance-measuring means.

[0083] According to the invention, therefore, the robot starting a taskcontinuously compares the distance measured by the odometer or otherdistance measuring device, with the distance from an earlier position tothe boundaries in the angular coordinate it is following. If theboundary is detected earlier than anticipated according to thiscomparison (or, in other words, if the difference between the distanceaccording to the map and the measured distance is negative), the robotcontinues to move until the boundary is detected. If the differencebetween the distance according to the map and the measured distance ispositive, or in other words, if the boundaries are encountered earlierthan expected, actual value of the coordinate is corrected to be that ofthe map.

[0084] The starting point will initially be the point “S”, andcorrection of distance errors will be effected relative to this point.As work proceeds, of course, the starting point may be updated to beanother point within the area, e.g., a meeting point with theboundaries, for comparison purposes with the map of the area

[0085] Similarly, the robot has been pre-programmed to avoid “islands”,but will detect an island according to the actual position of theboundary detected, and will correct its present working map based on thedetection of the boundary and the original map. As will be understood bythe skilled person, the larger the number of bounded areas, the higherthe precision of the correction of the actual working map., Therefore,the islands actually help in keeping precision and correcting the actualworking map. therefore, if the working area is particularly large, itmay be desirable to provide artificial islands for the purposes of mapcorrection.

[0086] As will be appreciated by the skilled person, operating accordingto the preferred embodiment of the invention described above is veryconvenient also in respect of the boundaries, since the wire or coil maybe embedded in the soil, thus avoiding any actual or even aestheticdisturbance to the working area, and the power requirements to generatea localized magnetic field are very small.

[0087]FIG. 4 shows an alternative embodiment of the invention, in whichthe location of each point is measured in Cartesian coordinates. As willbe appreciated by the skilled person, it is not essential to theinvention that any specific coordinates system be chosen, but it may bemore convenient to select a particular set of coordinates, depending onthe map correction process employed.

[0088] One particular process, employing Cartesian coordinates, will bedescribed hereinafter by way of example, with reference to theflow-sheet of FIG. 5.

[0089] In FIG. 5A the correction of an error on one axis (Y in theexample shown in the flow-sheet of FIG. 5A) is shown, according to onepossible embodiment of the invention, while the error in the other axisis not dealt with. FIG. 5B, on the other hand, shows a method accordingto another possible embodiment of the invention, in which both the X andthe Y errors are corrected in one step. It should be noted that,although only the error on one axis can be corrected at a time in theembodiment of FIG. 5A, the error on the other axis can be corrected bymoving in a direction perpendicular to the axis being corrected. Themovement of the robot can be programmed such that both the X and Ylocation coordinates are updated at a suitable rate of correction.

[0090] In FIG. 5B another preferred embodiment of the invention isshown, in which the boundaries are marked with markers (4 in FIG. 5B),which have a unique identity. The markers will typically be convenientlyevenly spaced, although any spacing scheme is possible. The markers canbe of any suitable type, e.g., and RF tag, magnetic tag or the likemarker, which emits a signal identifiable by a sensor. In such a case,of course, a suitable sensor, capable of identifying unique identitysignals must also be provided on the robot.

[0091] During the initiation process the robot performs a complete looparound the edge and memorizes the shape of the boundary as well as theposition of each marker (X,Y coordinates of each individual marker).This procedure allows for the correction of both the X and the Ycoordinates error, each time an edge is detected, according to themethod shown in the flow-sheet of FIG. 5B.

[0092] Schematically speaking, the robot will operate according to theflow-sheet of FIG. 6.

[0093] Reference is now made to FIGS. 7, 8 and 9 which illustrate afurther embodiment of the robotic lawnmower of the present invention. Inthis embodiment, the robot sweeps the space with overlapping straightlines by determining the location of the edge between uncut and cutgrass.

[0094] In the present embodiment, the lawnmower, labeled 20 in FIG. 7,additionally includes a plurality of sensors 22, each one measuring theheight of the grass in its general vicinity. FIG. 7 shows two areas, one24 of cut grass and one 26 of uncut grass. Thus, sensors 22 a and 22 bwill provide a high height output and sensors 22 c and 22 d will providea low height output.

[0095] By comparing the height output of the sensors 22, the controlsystem of the lawnmower can determine generally where the edge betweencut and uncut grass is. One embodiment of a sensor 22 is illustrated inFIG. 10 and described in detail hereinbelow.

[0096]FIG. 8 details the operations performed by the control system oflawnmower 20 and FIG. 9 illustrates the movements of the lawnmower 20 atthe edge of the lawn. While the lawnmower 20 is cutting a swath 25indicated by dotted arrows in FIG. 9, the sensors 22 continually measurethe height of the lawn nearby (step 30). The control system, with thenavigation system (compass and odometer), steers the lawnmower 20 in thedesired direction, as described hereinabove, while additionally ensuringthat the edge of the lawn is maintained in a desired location vis-a-visthe sensors 22. For example, it may be desired to cut a swath which isonly three-quarters the width of the lawnmower. For this situation, theedge between cut and uncut grass should be maintained between sensors 22a and 22 b or between sensors 22 c and 22 d.

[0097] The control system maintains the desired direction until the edgeof the lawn is detected, as described hereinabove. At this point, thelawnmower 20 must change direction of movement while keeping the properpercentage of uncut grass under the lawnmower 20. It is noted that thelawnmower can move both forward and backward.

[0098]FIG. 9 illustrates the change in direction. Initially, thelawnmower 20 moves in the forward direction along swath 25 (step 30).Upon reaching the edge, the lawnmower 20 performs an ‘S’ shapedbackwards maneuver, labeled 40, using the navigation system, until theedge between cut and uncut lawn is sensed between the desired twosensors 22. This step is indicated in step 32 of FIG. 8 and produces an‘S’ shaped cut in the lawn. As shown by line A in FIG. 9, the edge ofthe cut grass is maintained between the desired two sensors 22.

[0099] In step 34, the lawnmower 20 moves forward along the edge of thecut grass until the edge of the lawn is sensed once again. This movementis indicated by the short arrows 42 of FIG. 9. Finally, the lawnmower 20backtracks along the new swath 44. Initially and until reaching thelocation of the line A, the lawnmower 20 utilizes only the compassinformation. Once the edge of cut grass is found again (at the locationof line A), the control system utilizes both the compass and the sensoroutput to create the new swath 44. This is indicated at step 36 of FIG.8.

[0100] As discussed with respect to the previous embodiments, thelawnmower 20 has to return to locations of unfinished scanning, such aslocations on the opposite side of a flower bed or tree. To do so, thelawnmower 20 utilizes the navigation system to head towards the desiredlocation and, when it is close to the desired location, it additionallysenses for the edge between cut and uncut grass.

[0101] Reference is now made to FIG. 10 which illustrates an exemplarylawn height sensor. The lawn sensor comprises a rotatable wing 50connected to a potentiometer 52 via a pin 54 and a flexible joint 56. Aweak spring 58 is attached around pin 54 and extensions 60 of spring 58extend on either side of wing 50 and of a fixed pin 62. A cam 64 isconnected also to pin 54 and a microswitch 66 measures the movement ofcam 64.

[0102] The grass presses against the wing 50, which, since it is notheavy, will rotate. In turn, the wing 50 pushes against the relevant oneof extensions 60. Since the other extension 60 is maintained in place byfixed pin 62, the spring 58 is tightened, thereby providing a returningforce against the force of the grass.

[0103] The rotation of the wing causes the cam 64 and flexible joint 56to rotate, which rotation is measured by the potentiometer 52.Furthermore, if the wing 50 rotates too far, protrusions 68 of cam 64will press against a rod 70 connected to microswitch 66 which willindicate maximum travel of wing 50.

[0104] Reference is now made to FIGS. 11A and 11B which illustrate twoalternative embodiments of boundary markers and a sensor for detectingthe boundary markers located on the lawnmower. Reference is also made toFIGS. 12A, 12B, 13A, 13B, 14A, 14B, 15 and 16 which illustrateadditional types of boundary markers.

[0105]FIGS. 11A and 11B illustrate the lawn mower 10 with a boundarysensor 80 attached thereto. In FIG. 11A, the boundary is marked by aseries of markers 82 placed into the ground on the edge of the lawn.Typically, the markers are placed at set distances one from the next.Alternatively, they can be placed close together along portions of theedge which are very curvy and further apart along straighter portions ofthe edge. In FIG. 11B, the boundary is marked by a wire 84 which ismarked in some suitable and detectable manner. The type of markingmatches the type of sensor attached to the lawnmower 10.

[0106] In one embodiment, shown in FIGS. 12A and 12B, the boundarymarkers 82 have a magnet therein. In the embodiment of FIG. 12A, theboundary marker 82 is formed of a plastic pin 90, a magnet 92 placedwithin pin 90 and a plastic cover 94 covering the magnet-pin unit. Inthe embodiment of FIG. 12B, the boundary marker 82 is a metallic pinwhich is magnetized, as shown.

[0107] The corresponding sensor 80, for both embodiments, is a gaussmeter, such as the model 4048 manufactured by F.W. Bell Inc. of the USA,or any other magnetometer which senses the magnetism in the combinedunit. The distances between the boundary markers 82 are defined by thestrength of the magnet 92 in such a way that at any point along themarked perimeter, at least two markers are detectable by the sensor onthe robot.

[0108] In a further embodiment, shown in FIGS. 13A and 13B, the sensor82 is a bar code reader, such as the model 1516 from Intermek Inc. ofSeattle, Wash., USA. The corresponding boundary markers are, in FIG.13A, a white cable 96 with black bar code markings 98 thereon. The barcode markings 98 are located at fixed distances from each other. In FIG.13B, the boundary markers are pins (typically of white plastic) withblack markings 100 thereon FIGS. 14A and 14B illustrate a furtherembodiment which utilizes a Geiger counter, or other suitableradiometer, to detect the boundary markers. FIG. 14A illustrates a cable102 having a piece of a radioactive mineral 104, such as Americium,located thereon and FIG. 14B illustrates an individual pin 106(typically of plastic) having a radioactive mineral 104 thereon. Asuitable Geiger counter for use with lawnmower 10 is the SURVIVOR 200,manufactured by Bicron Inc. of the USA.

[0109]FIG. 15 illustrates a coil-capacitor circuit 110 incorporated intoa plastic or ceramic substance 112. Such a circuit 110 is then placedinto a pin unit such as pin 90 and cover 94 of FIG. 12A. Thecorresponding sensor 80 is a resonance tag reader such as the onesmanufactured by Checkpoint Inc. of Thorofare, N.J., USA, for anti-theftprotection in stores, such as clothing stores. The coil-capacitor unit110 can be similar to those manufactured by Checkpoint or any othersuitable coil-capacitor unit.

[0110]FIG. 16 illustrates a further embodiment utilizing transceiverunits 120. The transceiver unit 120 can be any suitable narrow bandtransmitting and receiving unit and is typically placed into a pin unitsuch as pin 90 and cover 94 of FIG. 12A. The corresponding sensor is asimilar transceiver. Each transceiver, within each pin, operates at thesame frequency and the sensor transceiver continually determines howclose it is to the nearest transceiver unit 120. When the sensortransceiver comes to within a predetermined distance, the sensortransceiver determines that it has reached the boundary.

[0111] For all of the above embodiments, the sensor 80 determines thatthe lawnmower 10 has reached the boundary when the signal sensor 80receives is at or above a threshold level which is calculated as theexpected reading five to ten inches from the marker or cable.

[0112] It will be appreciated that other types of markers and theircorresponding detectors are incorporated within the present invention.

[0113] All the above description and examples have been provided for thepurpose of illustration, and are not intended to limit the invention inany way. Many modifications can be effected in the method and devices ofthe invention, without departing from its spirit.

1. A method for automatically operating a robot within an enclosed area,comprising the steps of: providing a boundary along the perimeter of theworking area, the said boundary being detectable by a proximity sensor;providing boundaries along the perimeter of each area enclosed in theworking area, in which it is desired that the robot should not operate,the said boundaries also being , detectable by a proximity sensor;providing a proximity sensor positioned on the robot; providingprocessing means connected to the said proximity sensor and receiving aninput therefrom; providing location means on the said robot, todetermine the coordinates of the robot relative to an arbitrary origin,at any specific time; providing direction finding means; providing,memory means to store values generated by the said processing means and,optionally, by the said location means; causing, the robot to move alongeach of the boundaries provided around or within the said working area,to detect the said boundaries and to memorize their shape, and to storein the memory means values representative of the coordinates of the saidboundaries, relative to an arbitrary origin, thereby to generate a basicmap of the working area; when the robot is to operate within the saidarea: (a) causing the robot to start from a starting point having knowncoordinates within the basic map of the working area; (b) continuouslydetermining the coordinates of the robot by analyzing data obtained fromthe location means and by detecting the vicinity of a boundary; and (c)correcting the actual position of the robot on the basic map bycomparing the calculated and the actual coordinates of each detectedboundary.
 2. A method according to claim 1, wherein the boundarycomprises a metallic wire through which electric current flows, and theproximity sensor comprises a magnetic field detector.
 3. A methodaccording to claim 1, wherein the boundary comprises a guide wirethrough which an acoustic signal passes, and the proximity sensorcomprises an acoustic detector.
 4. A method according to claim 1,wherein the boundary comprises passive metallic means which is excitableby a magnetic field, and the proximity sensor comprises an electricfield detector.
 5. A method according to claim 1, wherein the boundarycomprises passive magnetic means, and the proximity sensor comprises amagnetic field detector.
 6. A method according to claim 3, wherein theacoustic signal is in the ultra-sound range.
 7. A method according toclaim 5, wherein said passive magnetic means comprises a plurality ofpins having magnets therein.
 8. A method according to claim 5, whereinsaid passive magnetic means comprises a multiplicity of magnets eachshaped into the form of pins.
 9. A method according to claim 1, whereinthe proximity sensor comprises a high contrast pattern code reader andthe boundary comprises high contrast pattern means.
 10. A methodaccording to claim 9, wherein the boundary comprises a two color guidewire having patterns of a first color at fixed distances thereon and asecond color for the non-patterned portions of the guide wire.
 11. Amethod according to claim 9, wherein the boundary comprises amultiplicity of pins each having a high contrast pattern thereon.
 12. Amethod according to claim 1, wherein the proximity sensor comprises aradiometer and the boundary comprises radioactive means.
 13. A methodaccording to claim 12, wherein the boundary comprises a guide wirehaving a radioactive unit placed at fixed distances thereon.
 14. Amethod according to claim 12, wherein the boundary comprises amultiplicity of pins each having a radioactive unit thereon.
 15. Amethod according to claim 1, wherein the proximity sensor comprises aresonance tag meter and the boundary comprises a multiplicity of pinshaving at least one coil-capacitive circuit therein.
 16. A methodaccording to claim 1, wherein the proximity sensor comprises atransceiver and the boundary comprises a multiplicity of pins having atleast one transceiver therein.
 17. A method according to claim 1,wherein the location means comprise movement measuring means.
 18. Amethod according to claim 17, wherein the movement measuring meanscomprise an odometer.
 19. A method according to claim 1, wherein therobot is coupled to a selected one of the group of: a vacuum cleaner, afloor sweeper and a floor polisher.
 20. A method according to claim 1,wherein the robot is coupled to a lawn mower.
 21. A method according toclaim 20 and including the steps of: providing the lawnmower with atleast a plurality of lawn height sensors; cutting a first swath of lawnin a first direction; performing a maneuver, under control of said robotand in response to output of said lawn height sensors, in a seconddirection generally opposite of said first direction to bring saidlawnmower to a location parallel to but overlapping said first swath bya predetermined percentage as indicated by the different output of saidlawn height sensors; cutting a second swath of lawn parallel to saidfirst swath while continually monitoring the lawn height output of saidlawn height sensors thereby to ensure that the percentage of overlap isgenerally maintained; repeating said steps of performing a maneuver andcutting a second swath for further swaths of lawn, wherein thepreviously cut lawn is denoted by said first swath of lawn and the swathto be cut is denoted by said second swath of lawn.
 22. A method forautomatically cutting a lawn, the method comprising the steps of:providing a lawnmower with a robot and at least a plurality of lawnheight sensors; cutting a first swath of lawn in a first direction;performing a maneuver, under control of said robot and in response tooutput of said lawn height sensors, in a second direction generallyopposite of said first direction to bring said lawnmower to a locationparallel to but overlapping said first swath by a predeterminedpercentage as indicated by the different output of said lawn heightsensors; cutting a second swath of lawn parallel to said first swathwhile continually monitoring the lawn height output of said lawn heightsensors thereby to ensure that the percentage of overlap is generallymaintained; repeating said steps of performing a maneuver and cutting asecond swath for further swaths of lawn, wherein the previously cut lawnis denoted by said first swath of lawn and the swath to be cut isdenoted by said second swath of lawn.
 23. A method according to claim 22and wherein said maneuver is an S shaped maneuver.
 24. A methodaccording to claim 22 and wherein said step of providing comprises theadditional steps of: providing a boundary along the perimeter of theworking area, the said boundary being detectable by a proximity sensor;providing boundaries along the perimeter of each area enclosed in theworking area, in which it is desired that the lawnmower should notoperate, the said boundaries also being detectable by a proximitysensor; providing a proximity sensor positioned on the lawnmower;providing processing means connected to the said proximity sensor andreceiving an input therefrom; providing location means on the saidlawnmower, to determine the coordinates of the robot relative to anarbitrary origin, at any specific time; providing direction findingmeans; and providing memory means to store values generated by the saidprocessing means and, optionally, by the said location means.
 25. Amethod according to claim 24 and wherein said steps of cutting comprisethe step of continuously determining the coordinates of the lawnmower byanalyzing data obtained from the location means and by detecting thevicinity of a boundary.
 26. A grass height sensor comprising: a housing;a rotatable wing against which grass can push, said wing having a pinattached thereto; a fixed second pin, connected to said housing; aspring attached around said pin, wherein the ends of said spring pressagainst opposite sides of said wing and opposite sides of said fixedpin; and means for measuring the angle of rotation of said rotatablewing.
 27. An automated robot for operation within an enclosed area,comprising: a proximity sensor positioned on the robot; processing meansconnected to the said proximity sensor and receiving an input therefrom;location means, to determine the coordinates of the robot relative to anarbitrary origin, at any specific time; direction finding means; andmemory means to store values generated by the said processing means and,optionally, by the said location means.
 28. A robot according to claim27, wherein the proximity sensor comprises a sensor selected from thegroup of: a magnetic field detector, an acoustic detector, an electricfield detector, a bar code reader, a radiometer, a resonance tag meterand a transceiver.
 29. A robot according to claim 27, wherein thelocation means comprise movement measuring means.
 30. A robot accordingto claim 29, wherein the movement measuring means comprise an odometer.31. A robot according to claim 27, which is coupled to a lawn mower. 32.A robot according to claim 27, which is coupled to a vacuum cleaner, orfloor sweeper, or floor polisher.
 33. A system for automaticallyoperating a robot within an enclosed area, comprising: boundary meanssuitable for positioning along the perimeter of the working area, and ofeach area enclosed in the working area, in which it is desired the robotnot to operate, the said boundary means being detectable by a proximitysensor; a robot provided with a proximity sensor; processing means onsaid robot, connected to the said proximity sensor and receiving aninput therefrom; location means on the said robot, to determine thecoordinates of the robot relative to an arbitrary origin, at anyspecific time; memory means to store values generated by the saidprocessing means; direction finding means positioned on the said robot,to determine the direction of travel thereof; and motion means, to causethe robot to move.
 34. A system according to claim 33, wherein theboundary means which is detectable by a proximity sensor comprises ametallic wire through which electric current flows, and the proximitysensor comprises a magnetic field detector.
 35. A system according toclaim 33, wherein the boundary which is detectable by a proximity sensorcomprises a guide wire through which an acoustic signal passes, and theproximity sensor comprises an acoustic detector.
 36. A system accordingto claim 33, wherein the boundary which is detectable by a proximitysensor comprises a passive metallic means which is excitable by amagnetic field, and the proximity sensor comprises an electric fielddetector.
 37. A system according to claim 33, wherein the boundary whichis detectable by a proximity sensor comprises passive magnetic means,and the proximity sensor comprises a magnetic field detector.
 38. Asystem according to claim 33, wherein the boundaries are provided with aplurality of individually recognizable markers.
 39. A system accordingto claim 38, wherein the markers are substantially located at evendistances from one another.
 40. A system according to claim 38, whereinthe marker comprises an RF tag or a magnetic tag.
 41. A system accordingto claim 33, wherein the boundary comprises passive magnetic means, andthe proximity sensor comprises a magnetic field detector.
 42. A systemaccording to claim 41, wherein said passive magnetic means comprises aplurality of pins having magnets therein.
 43. A system according toclaim 41, wherein said passive magnetic means comprises a multiplicityof magnets each shaped into the form of pins.
 44. A system according toclaim 33, wherein the proximity sensor comprises a high contrast patterncode reader and the boundary comprises high contrast pattern means. 45.A system according to claim 44, wherein the boundary comprises a twocolor guide wire having patterns of a first color at fixed distancesthereon and a second color for the non-patterned portions of the guidewire.
 46. A system according to claim 44, wherein the boundary comprisesa multiplicity of pins each having a high contrast pattern thereon. 47.A system according to claim 33, wherein the proximity sensor comprises aradiometer and the boundary comprises radioactive means.
 48. A systemaccording to claim 47, wherein the boundary comprises a guide wirehaving a radioactive unit placed at fixed distances thereon.
 49. Asystem according to claim 47, wherein the boundary comprises amultiplicity of pins each having a radioactive unit thereon.
 50. Asystem according to claim 33, wherein the proximity sensor comprises aresonance tag meter and the boundary comprises a multiplicity of pinshaving at least one coil-capacitive circuit therein.
 51. A systemaccording to claim 33, wherein the proximity sensor comprises atransceiver and the boundary comprises a multiplicity of pins having atleast one transceiver therein.
 52. A system according to claim 33,wherein the movement measuring means comprise an odometer.
 53. A systemaccording to claim 33, wherein the robot is coupled to a lawn mower. 54.A system according to claim 33, wherein the robot is coupled to a deviceselected from the group of: a vacuum cleaner, a floor sweeper and afloor polisher.
 55. A system according to claim 53 and additionallyincluding a plurality of lawn height sensors for measuring the height ofthe lawn and means for controlling said lawn mower to cut the lawn alongan already cut swath of grass.